Jump to content

sgl_imaging_challenge_2021_2.thumb.jpg.72789c04780d7659f5b63ea05534a956.jpg

if you had 35 pounds to spend


Recommended Posts

Before you jump for the TS Erfle, you maybe interested to know that its the exact same eyepiece as here

It's also worth noting that those ubiquitous 12mm widefields (which are basically just branded versions of eyepieces from United Optics <here>) are very pedestrian in terms of performance - as opposed to the BST Explorer 12mm, which Russ mentioned; a more highly-regarded eyepiece.

Link to post
Share on other sites
  • Replies 36
  • Created
  • Last Reply

Top Posters In This Topic

It's also worth noting that those ubiquitous 12mm widefields (which are basically just branded versions of eyepieces from United Optics <here>) are very pedestrian in terms of performance - as opposed to the BST Explorer 12mm, which Russ mentioned; a more highly-regarded eyepiece.

Jeremy is right. They are not the best corrected eyepieces and only really suitable for F6 (at a push) or slower. The BST Explorer is in a different class but just loses a little apparent field of view.

Link to post
Share on other sites

I'm planning on sticking to slow scopes for now, so no worries there... Are you sure the Adler / United Optics thing is the same eyepiece? The ones you are linking to are 60 degree EPs, while the TS one claims 70 degrees.

Link to post
Share on other sites

The United Optics ones actually claim "60 and "65" degrees (can't remember which ones in the range are which), and the problem is that apparent-fields-of-view specs are notoriously innaccurate and cannot be calculated mathematically. Therefore the AFOV than manufacturers claim can be "loose" to say the least :p

The only reasonable way to measure the genuine apparent field-of-view specification for an eyepiece is to use a method similar to David Knisely's one here <click> (the bit labelled "projection technique" is particularly cool.)

I'm planning on sticking to slow scopes for now, so no worries there.

That can help with the edge-correction, but eyepieces that are a bit soft on-axis can still under perform even in slow-scopes. I felt that the 20mm version of that EP wasn't as crisp as I'd hoped, even in an F15 scope...

I'm 99% sure the TS one is the United Optics one are the same EP - although note that coatings can be apparently differ, as eyepieces are supplied to order for each vendor who re-brands them. Hey, maybe even the field-stop can be widened to order too! :)

Edited by great_bear
Link to post
Share on other sites

Well, I've got a 60 degree EP and a 68 degree EP, so I'd know pretty instantly if the information online is misleading.

I guess TS could ask for a wider field stop from the manufacturer, but the field stop's function is to cut off the view when it starts to deteriorate.

I've emailed a local Dutch supplier asking about the true field of view of the EP.

Link to post
Share on other sites

To answer the original question, if I had £35 pounds to spend, I'd spend £90 buying a hyperion 17mm!

Gonna buy it tomorrow... :-)

With a fine-tuning ring, it will double as a 13mm or 11mm EP.

By the way, I checked with the Dutch TS Erfle supplier, and they say the EP definitely appears to have 70 degree AFOV.

Edited by Ags
Link to post
Share on other sites

I don't know about a 4" scope, but using a UHC I saw the Owl nebula as clearly from by suburban garden as I had a week earlier from a dark sky site where the filter wasn't needed. I was using a 6" f5 Skywatcher refractor though.

Apparently the UHC doesn't work on all types of nebulae.

Link to post
Share on other sites

I got the 17mm Hyperion today from Ganymedes (in Holland), and a 14mm fine tuning ring as well (giving an alternate focal length of 13mm).

First impressions were that the EP is very different to the 24mm - they may have the same brand but the 24 and the 17mm have different designs. The 17mm has a larger eye lens, which is not what you expect for a shorter focal length. And of course the 24mm has no Smythe lens. All the visible lenses look wonderful with excellent multicoatings.

So I now own the two smallest members of the Hyperion family.

Tonight was quite cloudy, but the moon was shining through so I tried the EP out at 17mm. What a perfect size for moon viewing (as you suggested great_bear)! It was easy to take in the whole disc and masses of detail stood out.

The moon is near perigee so it is quite large, so large that I did not try the 13mm option - I think the moon would have extended beyond the edges of the field of view.

The next dark night I will try out the EP on its other target: star clusters. There is still some time to see M34, M35, M36, M37 and M38 from my location, at least another couple of weeks before buildings get in the way.

Link to post
Share on other sites
  • 3 weeks later...

Finally had a dark night to try out the 17mm on M36 and M37. I'd say the 17mm feels more comfortable and is more immersive than the hyperion 24mm. The views of the two clusters were breathtaking. It was a difficult night though, with a malfunctioning celestron RDF and the mount's batteries running flat. I had to track the clusters down without the help of the goto system.

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.